Exciting times here in the Blondihacks boiler shop. As you may recall from last time, we got our boiler to pass the 150psi hydrostatic test. No small feat for our first ever attempt at this.

The running theme in that last article was how many decisions and actions made previously had come back to haunt me at the brazing stage. Things like not-perfectly-fitting ferrules, overly-large flat surfaces on cylinders, and so forth. We had one last action that would haunt us- the use of Loctite 569 hydraulic sealant on the electric heating element and thermoswitch (rather than its less nuclear cousin Loctite 545). The problem is that the 569 is a little too good, and after a few brief attempts, it was clear a great deal of force was going to be required to remove them. This is a feature rather than a bug, since these are the two largest holes in the structure, and it’s rather nice to know I never really have to worry about them leaking. However, I didn’t want to risk trying to remove them, because I was concerned about damaging the silver solder joints on their respective mounting bosses. The bosses have hex profiles on them so I can use a double-wrench approach, but I was concerned that might not be safe enough given how much force seems to now be required. In any case, the point of all this is that I was left with a problem. Allow me to explain.

After any silver soldering operation, the piece in question is left in quite a state. It will be covered in flux residue, misplaced solder, soot, heat discoloration, oxidation, the blood of the fallen, and general crud of mysterious origins. The usual solution to this is a pickling bath. “Pickling” is a colloquial term for soaking a part in an acid for a period of time to clean it up. Typically sulfuric acid is used for big jobs, or citric acid for things like jewelry. There are also more sophisticated products, such as Sparex, which is a sulfuric acid mixture that has some additives to help prevent pitting and other undesirable effects. Sparex is tailored to the type of metal, with “No. 2” being suitable for brass and copper.

Thus, the ideal solution (pardon the pun) here would be to mix up a very large batch of pickling acid and dunk the whole boiler in it for a while. However, I was concerned that the heating element and thermoswitch would be damaged by that, and as I just explained, removing them is now kinda off the table. Thus, I opted for mechanical cleanup.

You can see from this shot how much cleanup there is to do. The boiler doesn’t even look like copper and brass anymore. It’s a real fright.

I won’t lie, this was a lot of work. All told, I probably put around 20 hours of sanding, filing, polishing, scotch-briting, cleaning, etc into this piece. I won’t say it was the best way to do it, but I don’t really mind the work. Sometimes it’s nice to have a big block of mindless work to do, where you can put on a good podcast or music, and settle in for a while. There are no hard decisions to make, no machining mistakes to stress about, no fretting about materials or dimensions or anything. Just you, some sandpaper, a needle file, and time to let the mind wander.

In progress on cleanup. The vise with 3D-printed soft jaws was a great way to hold it at various angles while working on it.

Initial cleanup was done with files, picks, Scotchbrite, and 220 grit sandpaper. I then worked the sandpaper down to 400, 800, and 2000. I wasn’t going for a mirror-finish here. This is a working machine, not a trailer queen. It’s going to tarnish and get water-spotted from use anyway. I was just going for “nice”.

Here’s the final boiler, all cleaned up. This was pretty darned rewarding! It does reveal all the poor silver soldering I did, but let’s chalk that up to “artisan character”.

With all that work behind us, it’s time make some accessories! A boiler is more than just a tube that heats up water. It’s a system of elements that work together to efficiently process water and heat into energy that can do work. One of the most critical parts of that system is the water level. Water level management is a core skill of steam engine operation. If the level gets too low, the burner will overheat and something will get damaged. In my case, the electric immersion heating element must remain submerged or it will self destruct. If the water level is too high, it will contaminate the steam with too much moisture, potentially hydrolocking cylinders and causing other woe.

This makes the water gauge a critical bit of apparatus for the boiler. It’s not just a convenience thing for knowing when to put your toys away. It’s as important as the oil pressure gauge on an internal combustion engine (back when cars had gauges) and must be monitored at all times.

The core of the water gauge is a glass tube. This is low tech stuff. The glass tube is connected to the top and bottom of the boiler, to equalize the pressure and allow air to vent through it as needed. Sealing a glass tube against copper or brass piping requires some finesse, so there are a lot of fiddly components involved. I opted to buy a water gauge kit from PM Research rather than attempt to make this myself. In hindsight, it’s not that complex, really, and I could have done it. It’s nice to see how a proper one is built though, as reference for future DIY efforts.

Here are all the parts in the PM Research water gauge kit. It’s a lovely set, with very good instructions.

The gauge consists of elbow fittings at the top and bottom, with a glass tube in the middle. The tube has packing nuts that slide over it and compress gasket material against the elbow fittings to seal the glass. This is a primitive but amazingly effective system. The elbows will often have additional holes above and below for whistles, accessories, drain valves, or whatever you like. The true purpose of these extra holes is that it allows you to feed the glass tube in from one end while the fittings are attached to the boiler. This makes installing the gauge easy, because the elbows can be twisted into place first before the glass is installed.

Here’s where I got into some trouble. Remember way back when I was saying how it’s important to get the fittings on top and below the boiler exactly opposite each other? This is why. When you have elbow fittings coming off the centerline of the boiler, if that centerline is off, your horizontal pipe won’t be parallel to the horizontal plane of the boiler. If you have two such pipes, like in our water gauge, they won’t be parallel. This needs to be quite precise, because as any misguided finch knows, glass doesn’t bend. Furthermore, the horizontal extension pipes magnify any error in your fitting alignment. I got into a place where the glass tube just barely fit through the fittings, but the alignment was off enough that the tube wasn’t well centered in those fittings.

Here’s my first attempt at installing the water gauge. It looks quite lovely, but…

After installation, I tried filling the boiler with water. Because the alignment wasn’t perfect, the glass tube leaked. When I tried to tighten the packing nuts just a tiny bit to seal the leak…

PING! And water everywhere. Because the alignment of the fittings wasn’t perfect, the packing nuts weren’t applying straight-down pressure on the glass. They torqued it sideways a little bit, and there was no way to get them water-tight without shattering the glass.

I had a dilemma now. Fixing the alignment of the existing fittings was extremely difficult at this stage because the holes in the boiler are where they are. What to do? Well, if you can’t make it perfect, make it adjustable. What I needed was a flexible section that could be bent to get the water glass back in alignment.

The junk pile provided some ¼” copper tubing from an old refrigerator. A section of this seemed like the perfect thing to help align my gauge.

I cut a section of pipe and polished it up in preparation for silver soldering.

I needed fittings at the top and bottom of my new pipe to adapt it to the existing plumbing. Back to the lathe!

Starting with some generous hex bar, I turned down a shoulder for a 4-40 thread (to mate with the water gauge), cut the threads, and drilled it through.

The other end was going to silver soldered to the pipe, so it got a decorative filet and nothing else.

Here’s how the fitting fits on the pipe. This looks like it might just work!

Repeat for the other side and Bob’s your uncle.

A quick pass through the torch with some silver solder, and our flexible extension pipe is ready.

Here’s the extension pipe installed on the boiler. I reused the T-fittings that came with the water gauge, using one of them as a straight-through instead. I made plugs for all the extra ports I now had. A barely-perceptible bend in this copper pipe is all that is needed to bring the glass tube back into alignment.

Note in that last photo how the glass tube is now much too long. We need to cut it to length. This turns out to be really easy. All you need to do is file a small “nick” in the side of the tube with a triangular needle file. Then, wearing gloves and safety glasses, apply bending pressure at the nick with your thumbs. Just when you think surely the glass is about to explode into a million shards, forever scarring your entire body, it will “pop” into two perfect pieces. It’s kinda magical.

Something else of note here is the extra elbow I had to make to go under the new steam extension pipe. The fitting itself is uninteresting, except that it’s the one that made me a True Believer in Loctite 545. I don’t know what my mistake was exactly, but the threads on that elbow are a truly dreadful fit. The threads are so sloppy you can actually wiggle the piece with your fingers when it’s ostensibly tight. Shameful. Of course, it leaked like a fountain. A dab of Loctite 545, however, and it’s tight as a drum. The amazing thing is, the fitting is still loose, but still seals pressure while you wiggle it. Yes, Loctite 545 (and its burly cousin 569) is amazing stuff. I’m still going to remake that fitting for the good of the universe, but for now it’s serviceable thanks to whatever voodoo is in that little tube of 545.

With these changes made, the water gauge now seals perfectly and works like a champ!

I sized the new extension pipe so that the water level at the bottom of the glass is the lowest it should be allowed to go (when the heating element is barely immersed). About ⅔ of the way up the glass is the maximum fill point (before water starts to splash into the steam dome). This is a very usable range, even though the glass looks like it’s only covering a narrow range of the boiler’s capacity.

One of the final accessories we need is a “throttle” or regulator for steam pressure coming out of the dome to feed the engine. I’m using a simple globe valve purchased from PM Research for this. That’s not strictly the correct way to moderate steam pressure, but it’s reasonably effective for simple engines. However, I had another new problem.

Designing steam systems is very much an exercise in visualizing the clearance needed to install fittings. Everything has to screw in place, so you need to make sure the parts in question can spin the way they need to. You need to think about the order of operations of installing those parts to make sure it’s even possible to assemble. In this case, there wasn’t room to install the globe valve on the steam dome, because the valve stem didn’t have clearance to spin while the valve body was threaded on the steam dome outlet. An extension pipe would fix this, so it’s back to the lathe for yet another fitting. A steam fitter’s job is never done.

Starting with some small hex bar, I turned a nice diameter, cut 1/8-NPT threads on the end, and drilled it through.

The other end was tapped 1/8-NPT for the female part, and presto we have an extension fitting.

With this little extension pipe on the steam dome outlet, we can now spin the valve into place.

The final accessory we need is very important- the pressure gauge! I opted not to try and make this part, since it’s quite important that it be accurate. Once again, I went to the fine folks at PM Research for the part.

There’s an interesting aspect to pressure gauges- the siphon tube. You may have seen this before- there’s always an extra curl or loop of pipe in the connection between the gauge and the vessel. It looks decorative, but serves an important purpose. Measuring the pressure of a hot gas is tricky business, because hot gases can do a lot of damage. You need a gauge with a robust internal structure to tolerate that. There’s also the problem of pressure fluctuations. You want a gauge that reads a stable rolling average of pressure, not something that jumps around with every twitch. A siphon tube solves both these problems. The tube is filled with water, which serves to insulate the gauge from the hot steam. The tube also cools the water (because of its exposed length) and serves to condense any steam that makes it in there. The hot steam/water pushes on the cool water in the tube, which pushes on the gauge. This allows use of a much simpler and cheaper gauge for an otherwise demanding environment. Lastly, the mass of the water helps to dampen changes in pressure, creating a more even reading and thus a more useful gauge.

Here’s our siphon tube and pressure gauge installed, with a cameo from our new best friend Loctite 545. This is also a good look at some of my not-so-great brazing. I’m proud of it though, because of how much I learned, and how functional it is. “Pretty” will come with more practice.

The last thing I’ll talk about on this boiler is the simple-seeming problem of filling it. I made the fill plug as large as practical to make filling easy, but it still needs a funnel. I didn’t have the right size funnel on hand, but it occurred to me that I could 3D print one! This seems like a great application of that machine, and I’m always looking for excuses to justify the investment. In a few minutes I was able to lay out the exact profile I wanted in Fusion 360, hit Revolve, and fire it to the printer. Then the fun started.

My Printrbot has been pretty reliable as 3D printers go, but that’s a low bar. Consumer-grade FDM printers are not plug-and-play tools. Every time you use it, it’s practically a project in itself. Sometimes more than others. This time a lot.

My attempt to print the funnel started out okay, but it looks like bed adhesion failed about halfway through, and chaos ensued. That thick red slug at the top is solid plastic. I don’t know exactly what happened there, but it’s not good.

Well, I thought to myself, this happens sometimes. Prints fail, so you clean off the bed and start them again, and things are fine, right? Hoo boy.

The second print failed, but so so much worse. Somehow the plastic got backed up into the nozzle, filled the silicone heat shield, then proceeded to drive itself up and around the extruder.

By the time I caught this failure, the hot end was ruined. Everything was covered in burnt plastic slag and the whole extruder had self-destructed.

When the fancy toys let you down, it pays to go old-school. After all that, you know how I ended up filling my boiler? A cereal box and Gorilla Tape.

This funnel took 18 seconds to make and worked perfectly for weeks while waiting for new parts to arrive to repair the 3D printer. I am really trying to like 3D printing, but it continues to be a zippitty-do-dah toy and not a real tool when I really need it.

I got a new hot-end for the printer and installed it, but then it wouldn’t print properly. Test cubes on the new extruder were all coming out slanted vertically. Some analysis determined that the printer was skipping steps on the Y-axis, which generally means drive problems. I took the bottom end of the printer apart, and found the set screw on the Y-axis drive belt had stripped itself out, possibly when one of those print failures happened. Or maybe the failing Y-axis caused those failures. Hard to say. In any case, after some TLC, the Printrbot stopped pouting and did what I needed and produced a funnel.

I will say it was kinda worth the trouble, because this custom funnel that threads into the fill plug on my boiler is super sweet.

Totally worth it. At least, that’s what I’m telling myself.

Okay, that about wraps up this little adventure. With the accessories all built, we’re about ready to make some steam! Amazing! Stay tuned, because you won’t want to miss that. Trust me on this. Shit’s about to get cray cray.

After a marathon of brazing, it’s finally time for the big moment- hydrostatic testing. A boiler’s raison d’être is to make and hold steam under pressure. This pressure is potential energy which is used to power the attached engine. The funny thing about potential energy though, is that it doesn’t always go where you want it to. When the cat pushes your favorite vase off the shelf as an act of feline spite because you stepped on her tail last week, that’s potential energy being expended in an unscheduled fashion. Expending potential energy in an unscheduled fashion for a steam boiler generally means something done blowed up, and you’re probably contemplating your life choices en route to the emergency room. We want to be sure that doesn’t happen.

People figured out long ago that the way to prevent boilers from exploding is to do a hydrostatic test on them. The boiler is filled with liquid and pressurized to two or three times its normal operating pressure, then held there for a period of time. If the boiler can hold 3x normal pressure, you can trust it to hold lower pressures and not worry about standing next to it holding your spiteful cat.

The “hydro” is what makes a hydrostatic test relatively safe. An explosion is a runaway expansion of gas, possible because a gas can expand at very very high rates when so inclined. Incompressible liquids like water and oil can’t expand suddenly like that, and thus can’t explode. If there’s a failure of the vessel under a hydrostatic test, it will spring a leak and create a high pressure stream, but it’s basicially impossible for it to cascade into a catastrophic failure of the structure and subsequent explosion. That said, if you’re doing a high pressure test, there is still danger. If you’ve ever worked around heavy machinery, as I did for much of my youth, one of the first things they teach you is to never touch a hydraulic leak. Hydraulic hoses on farm equipment and the like typically operate around 10,000 psi. While they won’t explode (because liquid), the stream formed by a pinhole leak is immensely powerful, to the point that it can go right through your hand, injecting oil into your body and ultimately killing you. This is called a “hydraulic injection injury” and it’s most commonly caused by people running their hand over hydraulic lines to check for leaks.

Luckily, our boiler only operates at around 50psi, so a hydrostatic test to 150psi will suffice. A pinhole leak at that pressure is no picnic, but this is just water, and some basic precautions will suffice. For these tests, I’m wearing a heavy leather apron and eye protection. For the highest pressure portions, I upgraded to a full face shield and threw on a welding jacket for increased shrapnel and “unplanned pressure washer” resistance.

To run this test, we need a hydrostatic test pump. These can bought online in various forms and at various price points. They all work basically the same- there is a source of input liquid, and a hand pump which allows you to pressurize the fluid as it goes through. There’s a valve that allows you to close up the system and see if it holds pressure. If you don’t shut off the valve, the pressure will bleed back into your supply line, so you need a way to seal it all up and form a closed system.

The pump that I bought hooks up to a household garden hose, which is extremely convenient. I’m glad I spent a little more money for a nice pump here, because I would end up running this test many many times.

Here’s a picture of the pump I bought that I definitely didn’t scrape from Amazon without permission.

While the input is a garden hose, the output is a standard JIC hydraulic coupler (it came with the hose as well). I need a way to plumb this into my boiler, so it’s back to the trusty lathe. Any opening will do. I decided to use the ferrule for the safety valve, to save myself needing to plug that off for the tests. It’s 1/8 -NPT, so I need a very weird 1/8-NPT to 37° JIC hydraulic adapter fitting. The great thing about a lathe is that it gives one the ability to plumb anything to anything, including things one probably shouldn’t connect (such as a 600psi pump to a homemade boiler).

I started with some large hex bar stock. I drilled it out for the tap size of a JIC pipe thread, which is 1/4-NPT on the smaller hydraulic hoses.

This is a beefy tap by the standards of my tiny little machine shop, so I don’t have a tap handle big enough for it. Quality taps will have a center-hole on the end, which can be held by a tap follower. The tap can then be turned with a wrench.

At this point my brain went on a several-hour vacation. For some reason, I decided I needed to turn the 37° flare for the hose fitting, which I really didn’t. It’s a male fitting, so it will still seat just fine at the bottom of my adapter (which has a large-to-small change in diameter halfway down). Then for some reason, I decided the flare should go on the boiler end of the fitting. Then for some reason I decided it should be a male flare, the same as the hose that ostensibly seats against it. Then for some reason I set up the lathe’s compound backwards anyway. That’s a lot of “then for some reason” moments all in one. Luckily, none of these mistakes turned out to matter one iota, save for 30 minutes or so of wasted time.

In any case, I blithely set up my lathe to turn the taper using the compound-feed method. This means setting the compound to one half the desired angle, then using it for the length-wise feed instead of the carriage. This is a super easy way to make short tapers (limited to the travel of the compound, which isn’t that much on many smaller lathes).

Here I am very carefully setting up to cut the wrong 37° angle on the wrong end of a fitting that doesn’t need it anyway. There’s one teachable moment though- I’m using the protractor against the chuck face, and shining light up from below. When no light gets through, I know the angle is perfect. Never trust the angle marks on the compound when it really matters.

Here’s the final fitting. Note the pointless taper on the small end. The large end doesn’t have a flared seat inside for the JIC hose fitting, but some Loctite 545 hydraulic sealant on the threads was more than enough to keep it pressure-tight.

Amazingly, despite all the mistakes, this fitting gave me no trouble at all during pressure testing.

In addition to the adapter, I also needed to make a few plugs and caps for all the openings on the boiler. I wanted to eliminate variables in the first test by testing without any accessories installed. Also, some of the accessories (such as the pressure gauge) would not tolerate the 150psi test pressure. For the large openings (the thermostat and heater) I had to use the components themselves as plugs, because I didn’t have the ability to make blanks that large.

Here we are with all the openings plugged, and ready to test.

With the adapter installed, the very first thing to test is simple- does it even hold water? Given what an inexperienced brazer I am, this is by no means a given. I was actually pleasantly surprised when it did! I was so busy looking for problems that I forgot to keep an eye on the filling operation, as you can see in this video.

That video also shows the basic operation of the pump. It has a flow valve which is handy for filling the vessel and controlling the velocity of pressure buildup, and then the large pump handle is used to increase pressure above that provided by the water source.

Since the vessel appears watertight, the next step is a “low” pressure test using just the pressure from the garden hose. In other words, open the flow valve, let the hose fill the boiler, then leave the faucet on. That will hold the vessel at household water pressure, which is generally around 40-60 psi in North America.

This is the first “real” test of the boiler, and it performed…. poorly. I closed up the fill plug (it was open to evacuate air during filling), then as you can see in this video, started easing the valve open under household water pressure.

If you look closely (The water is hard to see on video), you’ll note that I tried to build a steam boiler, but have in fact built a sprinkler system or carnival water feature of some sort. I expected a leak or two, but there were more like twenty. Almost every single fitting leaked, several in multiple places. Both heads had multiple leaks on their seams. The video ends abruptly because I was so disgusted with this result that I had to walk away for a while and collect my thoughts. In my experience, this is the best way to handle frustration. Take a break, get away, and go do something else. Attack the problem when you are fresh and your head is clear.

I had a lot of leaks, that much was undeniable. There was really nothing to do but get out the torch and start fixing them. This started a cycle of:

I went through this process literally dozens of times. Sometimes I reduced the leak count with one of these iterations, and sometimes I didn’t. Once or twice, I even created new problems. This went on for weeks. For the bigger seams, like the boiler heads, the oven preheat I mentioned last time was used, which further complicated things (but saved a lot of torch fuel and time). I won’t lie- this was a deeply, deeply demoralizing process. After a few failures in a row, I would have to take a break. A couple of times I had to stop for a week and get some space from the situation. Slowly but surely, however, I did. Make. Progress. That was what I had to keep reminding myself to keep my spirits up. Despite the constant feeling of “two steps forward, one step back”, progress was measurable. A big milestone that really helped morale was when I got the head seams sealed up and only the fittings were left. That was a big deal, because it proved that I really can do this. Those are the toughest joints to get right, so once I did, the rest felt possible. Difficult, but possible.

The boiler seams were fixable by thoroughly cleaning the joints, sanding them down, then brazing over top of the existing silver solder. For most the of fittings, I used needle files to file down the joints until the source of the pinholes were revealed, then silver soldered over them.

One tough nugget was the steam dome. After my first attempt, I had to completely redo it by filing down all the seams until I could break it loose, sand and clean the whole area, and solder it all up again. After one cycle of this, I was able to repair the remainder of the dome leaks with the file/clean/solder-over method.

Here’s my second attempt at the dome. Not pretty, but gosh darn it, it’s pressure-tight now.

Painful though it was, I learned an incredible amount in this process. Not just about silver soldering, although this was definitely an into-the-deep-end crash course in brazing. I also learned other interesting things about pressure sealing. Teflon tape is way less effective than I used to think, for example. I also learned that Loctite hydraulic thread sealant is amazing stuff. There are a lot of types of it though, so you need to do some homework. The most generally useful is Loctite 545, which has an almost superhuman ability to seal any crappy fitting against pressure. Another option is Loctite 569, which is designed (I think) for higher pressures. Since writing this, I have seen Loctite 545 make some truly dreadful fittings work properly. It’s a steam engineering miracle, that stuff.

As leaks get fixed, you gradually get to a point where more and more pressure is needed to reveal the next leak. For a long time, I had many leaks as soon as the household water pressure started to hit the boiler. I needed to get to the point where the household pressure was completely contained with no leaks before I could start using the pump to actually get to the final hydrostatic test pressure.

A particular trouble spot at household pressure was the large boss for the heating element. It’s a tapered thread 1.25″ in diameter, and it was made from a commercial fitting I bought on Amazon. This fitting was of very poor quality, and I could never get it to seal properly no matter how tight I made it. It got to the point where I couldn’t advance my pressure testing any further because of this. However, after I put a little Loctite 569 sealant on the threads, it never leaked again. It’s remarkable stuff. Unfortunately, I learned later that 569 is designed for small diameter threads, because of the strength of the bond. Removing this heating element (should I ever need to) will, unfortunately, be quite difficult now.

However, I now got to the point where I could start applying positive pressure with the hand pump, to work our way up to the goal of 150psi (Three times operating pressure for this boiler).

Eventually, I was able to work my way up to around 50psi, and I got down to one remaining nemesis. That damned fill plug. Remember that thing? The one where I had to open up the hole with a round file, so the fit wasn’t perfect? And the one where the fitting on was on the large side for sealing against a curved surface? Yah, that one. I mentioned how I had made dozens of passes trying to seal leaks on the boiler. On almost every one of those passes, I took a shot at fixing the fill plug. No matter what I did, the damn thing continued to leak at around 50 psi. I completely filed down the joints and redid them three times. Nothing worked.

Eventually, I went back to the source material for help. D.E. Johnson’s design in Live Steam magazine (upon which this boiler is based) had a small blurb at the end about dealing with leaks. He suggested using plumbing solder here and there as needed. Plumbing solder is not, strictly speaking, rated for high pressures. However, for a small pinhole area in an application that will never see above 60psi, it should be totally fine. It’s also an order of magnitude easier to fill a gap with plumbing solder than with silver solder. So, feeling a little dirty, I busted out the plumbing kit and starting making attempts to fix the fill plug with it. It took a couple of more iterations of filing and cleaning, but in the end the humble old plumbing solder did get it done.

For these last few repairs, I had to stop using the oven to preheat for a brazing operation, because I didn’t want to chance removing the now very installed heater. The heater would likely be damaged by the oven, so that was out. Because I used the “strong” sealant, removing it will take a pair of, shall we say, extremely non-trivial wrenches. I don’t want to risk putting stress on the braze joints for the mounting boss, so I stuck to localized heating with the oxyacetylene torch for all remaining braze operations. The boiler shell still gets very hot all over from this, but I was basically gambling on not overheating the electrical components. Luckily, they are tough and survived just fine.

With the fill plug finally resolved, here we are holding 50psi. You’ll notice a lot of towels and buckets in these pictures. This is a very very wet process. You will cover the whole area in water no matter how hard you try to be neat.

Things got really exciting now. I upped my safety game a bit (adding a full face shield and leather welding jacket to the mix) and started aiming for that 150psi in the sky.

Above 50psi, interestingly, the leaks changed character. At low pressure, the leaks were like jets or sprinklers. By the time I made it to 100psi, however, the leaks were much much smaller, and they turned into slow seepages. They were like little wet areas that appear as if from nowhere. It can take some real study to figure out where the true origin of a wet spot is. It may be under the spot, or it may above it and collecting where you see it. Adding brightly colored dye to the water can help with this. This is important, because you don’t want to waste time filing, cleaning, fluxing, and resoldering an area that isn’t where the defect actually is.

Is that 100psi? Why yes, yes it is.

Around 100psi, a new seepage appeared in a tricky area where I had filed down the side of the heating element boss to make room for one of the head stays. There was a very tight space between them that I never got a good dose of solder into. I ended up kind of smothering the whole area between the two fittings, and hoping I got it. I mostly did.

150 PSI!!!!!

When I hit 150psi and the boiler was still dry as a bone, this was an incredible, incredible feeling. Moments like this are why you should take on hard things. The harder the challenge, the greater the payoff. I’m writing this weeks after the fact, but I still have a warm fuzzy glow from this achievement. I almost can’t believe I managed to build a complex pressure vessel from scratch that holds 150psi like a boss.

The goal was to be able to hold 150psi for 30 minutes, so I started the clock. Truth be told, that last tricky area I mentioned still had an absolutely microscopic flaw somewhere, and some moisture did collect there over time. In 30 minutes, the boiler lost about 10psi. The lower the pressure got, the slower the decay, however. That microscopic flaw, wherever it is, needs north of 130psi or so to be revealed. I decided this was more than good enough and proceeded to pour many many celebratory beverages of dubious moral character into my face.

Here’s a nice little video tour of the steam boiler I made with my bare hands, holding pressure like a goddam boss.

We’ll end on that high note for the moment. We have accessories to make before we can use this boiler to run an actual engine, but the finish line is so close we can TASTE IT, people. Stay tuned.

After months of making parts, we’ve finally reached the point where we can start assembling this boiler. Now we have some brazing to do. A lot of brazing.

This process is also sometimes called “silver soldering” because the process very much resembles soldering, except the solder has a very high melting point. Silver solder has a fair amount of actual silver in it, which is the secret to its strength (and price tag). This is not to be confused with plumbing soldering, which is a much lower temperature process. That’s sometimes called “soft soldering”, but not to be confused with electronics-type soldering which is a different thing once again. This stuff can be tricky to self-teach because there are a whole family of vaguely-related processes that all have a variety of names (that also vary by country). Googling it is difficult because you may not know exactly which process you’re reading about. I’m choosing to call this “brazing” here because I think that more accurately reflects the scale of the process. It’s more similar to, say, repairing a crack in cast iron with a bronze welding rod than it is to soldering a circuit board.

Anyway, I was pretty nervous about this portion of the job, because I’m not a very experienced brazer. I’ve only done it a few times, and only at small scales. This is jumping way into the deep end of the learning curve for brazing. The boiler is a large work piece, and all the joints have to be perfect or it won’t hold pressure. I swear this seemed like a good idea at the time, but we’re about to embark on the most painful project road I’ve been on since Veronica’s graphics board.

To start with, I decided to install the small fittings in the shell. We have ferrules for a blow-down valve, water gauge, fill plug, and safety valve. Then there are some elaborate holes for the steam dome. Before I can install anything, I need to make the holes in the shell. After months of it sitting on the bench, I’m finally going to do something to this shell!

The layout for these holes was actually pretty challenging, and truth be told I didn’t do it very well. The trick is getting two centerlines down the axis of the boiler, exactly 180º apart. It doesn’t matter where on the shell they are, it only matters that they be precisely opposite. This matters more than you think, because it governs the angle at which the fittings stick out of the boiler. Not only does it look weird if the fittings are crooked, but for the water gauge, the attachment points need to be parallel above and below the shell. This will haunt me later.

I did the layout very similar to how it was done for the legs. I applied layout dye to the relevant areas, then used a height gage and some creative piles of precision blocks on the surface plate to line things up.

The drilling jig we made waaaay back in part 1 of this series is finally going to pay for itself! It did indeed work very well for holding the shell in the drill press.

The first hole I drilled was for the blowdown valve. I started on the bottom, because it’s less visible. If there’s any step in this process that needs practice, I want to do it there.

The holes are drilled slightly undersize, and then opened up carefully with a tapered hand reamer. This ensures a very good fit with the ferrule. A good fit helps ensure success with the brazing operations to come. Silver soldering a perfect seam is much easier than having to fill a crappy one. Much like welding, painting, and bank heists, the preparation is really the most important part.

The rest of the ferrules followed this same process, so I won’t show them all here. Two other accessories were more interesting, though- the fill plug and the steam dome.

When I planned the fill plug, I wanted it to be comfortably large, because you need to pour water into that opening. However, if you make it too big, it’s difficult to install because you end up with a large flat area being attached to a cylinder. The seam gets larger the larger the flat thing is (and the smaller your cylinder radius is). That’s why the steam dome had to be carefully fitted.

When I chose the size, I didn’t think ahead to what drills I actually have, and wound up having to buy this large reduced-shank bit for this hole. The copper is very grabby, and my cheap drill press doesn’t really go slow enough for a bit this large. I clamped the heck out of everything and went as slowly as I could, but it was still dramatic and the hole is a bit messy.

The next unexpected problem is that the fill plug is too large for my tapered reamer trick to work. A larger tapered reamer is very expensive, so I opted to open up the hole with a circular file instead. This worked, but the fit is not as good as the other fittings, and that would come back to haunt me big time later. Noticing a theme here? A lot of things I did at this stage made later parts of this a whole lot harder. Learn from my mistakes.

A round file seemed to do the trick for fitting this piece. However the large size and less-than-perfect fit here would make it really difficult to prevent leaks on this fitting. There’s gonna be some awfully bad language here later on. I’ll spare you the direct transcript, but take my word for it.

After all the basic holes were done, it was time for the steam dome. This area consists of one large hole in center for the dome stay, and two rings of small holes which form a primitive steam separator. The dome stay, you may recall, is there to reinforce the braze joint of the dome on the boiler, since the joint is in tension. Silver solder is strong in shear mainly, so the stay is good insurance. The little holes form a sort of screen to keep water out of the dome and hopefully collect mostly dry steam.

To do this layout, I used a bolt-circle calculator and a compass.

Most online bolt-circle calculators are designed for DROs on mills, so they give you a series of X/Y coordinates for each hole. This is completely useless for doing layout by hand. If you search around, you can find calculators that give you the chord length between holes. This allows you to set a compass and walk your way around from one hole to the next. I like this one (PDF). That’s a nice one-pager you can hang on the wall.

At this point, all the fittings are made, and the holes are drilled. It’s time to start brazing! Since I’m still pretty new at this, I opted to do some practice on scrap first.

I brazed these two stubs together just to make sure I still knew how to do this.

For a heat source, you have a lot of options when it comes to brazing. Some jobs can be done with a plain propane torch, like you might use for plumbing soldering. Really small jobs, such as jewelry, can be done with a chef’s torch. Larger jobs are better suited to something like Map/Pro, which burns quite a bit hotter than propane. These are the yellow bottles at the hardware store. People often call these MAPP gas, but that’s not technically correct. MAPP gas was a sort of acetylene byproduct that existed because one of the companies making industrial gasses found a niche for this waste product. It was fantastic, but it stopped being produced in 2010. Industry found a use for it, so the company that made MAPP no longer sells it in little yellow bottles in the hardware store. The Map/Pro gas you now get is propane with some additives in it to burn a bit hotter. It’s still better than propane, but not the beast it used to be.

Of course, when you need the true unholy fires of hell, there’s only one choice- oxyacetylene. More on that in a moment. There’s another interesting budget alternative- propane/oxygen torches (sometimes called oxypropane). Propane is a lot cheaper than acetylene, and still burns hot enough for most jobs when fed oxygen through a gas-mixing torch. That said, oxyacetylene is not all that expensive, and still the king for big jobs.

I decided to start by assembling one of the heads. All the stays, ferrules, and fittings can be brazed into one side, and the Map/Pro torch worked okay for this job. It takes some time to get the heat in and it makes a lot of soot, so everything is black when you’re done. Map/Pro is pretty hot, but it doesn’t burn clean because there’s only ambient oxygen for it to use. The flame is “running rich”, to borrow an automotive term.

For each braze joint, I thoroughly cleaned everything, then applied generous amounts of flux.

Here we are all ready to braze in the heater boss, an accessory ferrule, four stay bushings, and the head stays themselves.

The head was a bit of a struggle, but I got it done. The challenge was getting enough heat into things. Much like soldering, the secret to brazing is that the part has to melt the solder, not the heat source. That means you have to get the whole part hotter than the melting point of the solder, which for silver solder is quite high indeed. I got it done, but it took a while. If your heat source isn’t big enough, you can reach a local maximum where the part is bleeding heat into the air and table faster than the torch can supply it. Remember from school that temperature conducts through something faster the higher the gradient is. The hotter the part is, the faster heat bleeds out of it. That means it gets exponentially harder to raise the temperature. That’s why you need a torch that burns at thousands of degrees to braze with solder that melts at only hundreds.

This should have been a warning sign to me that the Map/Pro was going to let me down. I don’t know why I thought I could do something bigger, considering what a struggle the head was. Sometimes you get fixated on a plan and it blinds you to the problems.

I moved on to the fittings in the boiler shell next. When brazing a large piece, you need to preheat the whole mass, to prevent that large temperature gradient I mentioned. If the whole piece is cold, the joint area will never get hot enough, because the heat will keep conducting away into the colder areas and you’ll be there all day. This is especially true with copper, which is an incredible conductor of heat.

Knowing this, I started preheating the boiler and waiting for it to get hot enough that I could get the joint areas up to brazing temperature. And I waited. And waited. And waited. After half a tank of Map/Pro, I didn’t seem to be getting there.

I even tried a ceramic blanket covering part of the boiler to try and hold in the preheat, but still the boiler hit a temperature ceiling that was too low to braze the joints. You can see the mess I made trying.

What I ended up with from this attempt was a messy couple of joints that weren’t properly bonded at all. They were so bad as to be unsalvageable, so it was with great regret that I had to drill them out and make new parts.

This was painful to do, but I had no choice. These parts were ruined by repeated attempts to braze at too low of a temperature.

Each of these failed attempts was expensive time-wise. Not only did I have to drill out the fittings and machine new ones, but the whole area of the boiler had to be cleaned up again. Braze joints must be spotlessly clean! This meant a lot of scrubbing, sanding, scraping, and muttering of words that my mother did not teach me.

At this point, I couldn’t deny reality any more. It was time for the Big Big Fire.

Small oxyacetylene setups like this can be had pretty inexpensively. Once you have the tanks (which cost a fair bit up front) refills (actually tank exchanges) are quite affordable. For a small shop just doing occasional brazing or heating jobs, these little tanks are great. If you’ll be doing a lot of cutting, welding, etc, get the full-size tanks.

Oxygen and acetylene tanks are one of the few things you can’t buy online (due to shipping regulations) so you’ll need to go make friends with a local welding gas supplier. Sometimes they’re super nice, and sometimes they’re super mansplainey. Your mileage may vary, but I’m fortunate to live close to a great shop.

A few words of safety on these things is probably in order. Personally, I choose to store the tanks in an outdoor cabinet. I have had the valves on them leak in the past- these tanks are (very) recycled and sometimes (often) they get abused. Not by me, or you, or any of our friends, but someone out there is abusing everything. A cloud of acetylene in an enclosed space is a bomb, and that’s a conversation you really don’t want to have with your insurance company. More than once I have opened my outdoor cabinet to the distinct smell of acetylene in the air, despite the valve being as tightly closed as I can get it.

Oh, and… uh… be careful where you point it. The first rule of gun safety is don’t point the barrel and anything you don’t wish destroyed, and the first rule of torch safety is don’t point it in the direction of anything you don’t wish to be molten slag. Especially the hoses! Be very mindful of where your hoses are in relation to the white hot finger of god coming out of the torch.

When lighting the torch, the rule of thumb is “Fuel First On, First Off”. You light the torch on acetylene only, and when you’re done you shut the acetylene off first so the oxygen will blow out the flame and clear all gas out of the torch. This prevents the flame from flashing back up into the torch, and potentially even the hoses (which would be a pretty bad day).

The final safety thing I’ll call out is safety glasses. The killer with these torches is not ultraviolet like with welding, but rather infrared. The torch makes enough infrared energy to hurt your eyes, so wear appropriate IR safety glasses. They look like really dark sunglasses and turn the world a bit green. A pair may have come with your torch.

The rule of thumb for these small torches is to set your acetylene to 5psi and oxygen to twice that (10psi). Adjust the regulators so they read 5 and 10 respectively, with the torch valves open (the gauges read artificially high when the torch is closed) The oxygen tank valve should be opened all the way, but the acetylene tank valve should be opened three-quarters of one turn only. Then you crack the fuel valve on the torch, light it with the sparker, then crack the oxygen. Experience will give you the right ratio of the two, but you’re looking for a large blue flame with a little point of white flame at the base. You can go by sound as much as anything. It should be “hissing”, but not like a roaring jet. This is all pretty forgiving, though. If your acetylene is way too high, the flame will be dirty and leave soot on everything. If your oxygen is way too high, it’ll “blow out” the flame and die. Anything between those extremes will work fine until you gain experience with the subtleties.

The neutral flame is what you’re aiming for. The second one is too much oxygen characterized by a roaring jet sound, and the bottom one is too much acetylene. Image courtesy of The Welding Institute UK.

Here’s the process of lighting the torch. It’s very exciting and easily the most thrilling tool in the shop.

Back to our boiler. The method I’m using here is to pre-heat the body of the shell for a while with the torch, and when there’s a good amount of heat in the shell (to keep that temperature gradient down), you can go in and heat the fitting a bit, then hit the joint directly for a couple of seconds with the white tip in the flame. You’ll remember from science class that this is the hottest part. Then get in there with the silver solder, while holding the heat on the metal, but away from the solder. Again, the key is to get the parts to melt the solder, not the torch. The solder will flash around the joint instantly, like magic, once the temperature is high enough. Always keep the torch moving. Oxyacetylene is powerful stuff, and you’re likely to melt anything you hold it on for more than a few seconds. Particularly your face. Always aim away from face.

With the big big fire, brazing in the fittings on the bottom of the tank went very well. The secret is to hold the vast majority of the heat on the shell, where the majority of the mass is.

Be very careful about overheating the small brass fittings though, which is easy to do with this much torch. Here I’ve melted the fitting, and have no choice but to drill it out yet again.

Heat control is really important in a situation like this, where the parts being brazed have a very large difference in mass. The boiler shell can suck up seemingly infinite heat, whereas the little brass fittings melt if you blink at them funny. Ask me how I know. Then ask me why I’m so good at sanding. Then ask me where I learned all those terrible, terrible words.

Sure, it’s frustrating to see all your machining work get destroyed this way, but you gotta learn somehow.

With all the fittings brazed in, it was time for the heads.

The heads are a bit tricky to hold in the correct position for brazing, so I made a strut that goes inside the boiler, and clamps to the larger openings in each head.

I welded some scrap into an S-shaped clamp that would hold a threaded rod through the center of the boiler, attaching to the large ferrules on each end with some clamping nuts and fender washers. The hardware pieces were all smaller than the largest opening on the boiler so I could shake them out when assembly was complete.

Since the heads are so massive, I felt that pre-heating the whole boiler was in order. I preheated my kitchen oven to 500°F (as high as it will go) and put the fluxed boiler/head assembly in there for 10 minutes. This worked really well and saved a lot of preheating time with the torch.

What’s cookin’? Steam boiler.

I had my brazing area all set up ahead of time so I could scoot the boiler over there immediately from the oven and get the torch on it before the preheat was lost.

Here’s some video of brazing one of the heads, to show the general technique. You can see that after flash-heating the joint itself with the hottest part of the flame, I’m holding the heat on the massive outside of the shell while applying the solder to the inside seam. The heat is all going to bleed out through the much more massive shell, so that’s where the new heat needs to go. The much less massive head will stay hot by conduction, and both parts will melt the solder.

Brazing the first head seemed to go quite well. Here you can see the clamp holding the head in place, made from some welded scrap.

Here’s another angle, showing how the procedure went.

The second head was done another day, so I had to pre-heat again.

Here we are fluxed up and ready to go in the oven for the second head.

Note that for second head, we’re also brazing all the head stays on that end at the same time. The ferrules have to be threaded on to the stays, then brazed into the holes, then the threads brazed to the ferrules. By now we’ve already brazed them at the other end, and thus nothing on that end will turn anymore.

After we’re done, the head is literally a hot mess, but amazingly it will clean up nicely.

Normally at this point, you might put the brazed parts into a pickle bath (a medium strength acid like Sparex No. 2) to clean up all the old solder crud, flux, soot, etc. Pickling solution does a very nice job of this. However, I decided to wait until after pressure testing, since I’d need to make a mess again if there were leaks to repair. This is yet another decision that would haunt me.

That’s it for the brazing! Or is it? This is the beginning of quite an odyssey, so stay tuned next time for more boiler action.

Last time we roll-formed some copper stock to form the heads, and that was pretty cool. We have a few more operations to do on those pieces, and we need to make all the head-related accessory parts for our boiler.

First up are the stays. A “stay” a very steam-engineer word that usually means “a rod that keeps something else from exploding”. In this case, the something else is our heads. Thus these are “head stays”. The main body of the boiler is a cylinder, which is an inherently strong structure. Circles are really good at containing pressure. However, the heads are flat at the ends. They are a theoretical weak point in the structure. As I’ve stated before, I think Mr. Johnson’s boiler design is rather overkill for the 50 psi working pressure it will see, but I also acknowledge that no part of me is a mechanical engineer and I know basically nothing about pressure vessel design. I’m taking his word that these head stays are necessary. The head stays take the form of four copper bars that run the length of the interior, threaded into brass bosses in each head. This ties the heads together and also ensures the pressure isn’t being contained solely by the braze joints on the heads.

I purchased ¼” copper bar stock remnants from eBay. They’re quite lovely! Copper is a very attractive metal, though a bit spendy and tricky to machine.

As I’ve mentioned before, eBay is my go-to for metal stock in small amounts these days. Thanks to flat-rate USPS shipping boxes, most sellers offer free shipping, even on rather substantial chunks of steel and iron. The other day, I received a 20lb steel bar in a flat-rate envelope. Roughly 47 envelope molecules survived the journey, but the 20lb steel bar was fine because it’s a 20lb steel bar. I feel bad for everyone else’s mail in that vicinity, though.

The first task for our lovely copper stays was to thread the ends ¼-20 for the mounting ferrules. Threading copper is really difficult, however. A threading operation involves a lot of tool pressure. The die is cutting multiple threads at once, and it relies on the strength of the previously cut threads to pull the die forward as it cuts new ones. Copper is highly resistant to being cut this way, and isn’t quite strong enough to push the die forward through itself. So it’s both too tough and too weak, in the exact wrong ways. My solution to this was to turn the ends of the bars 5 thou under-size, chamfer the ends generously (to help the die start), use lots of cutting oil, and apply a lot of forward pressure on the die. Even with all that, there are decent odds the threads self-destruct partway through if the die gets hung up.

Another option would be to single-point cut these threads rather than using a die. However, these bars are very thin. Probably too thin to hold up well to the high tool pressures needed to machine copper.

It was no picnic, but I did manage to get ¼-20 threads cut on each end of each stay.

Next up are the ferrules. These are brazed into holes in the heads, and the stays are threaded in to them. We need eight of them, so it’s mass production time.

I marked out all the diameter changes on a batch of four ferrules. I added an additional zone between each one, the exact width of my parting tool.

I’ve mentioned this parting-tool technique previously, but it was extra useful here. Using a wide parting tool, you can plunge into the work to the depth needed for final diameter, and make a note of the dial reading on the cross-slide. You can then cut the rest of that diameter by winding out past the backlash, then coming back in to that same dial reading on each ferrule. It’s the poor-person’s DRO.

Repeatability is what machine tools are all about. Using the same dial reading each time, the diameters are formed by plunging over and over again. This is a very efficient way to turn out a batch of shouldered bushings.

I did two batches of four. I didn’t want to do a batch of eight all at once, because the unsupported stock area in the lathe got pretty large, and the parting-tool-plunge technique requires good rigidity in the setup. This might be a good use-case for a follow-rest!

With the profiles cut, I then tapped all four at once as well.

Profiled and tapped, we can now part off each one using the waste zone we marked between each ferrule.

The final step in our production line- each one gets parted off and thrown in the finishing bin. If it was 1890, we just earned ourselves 4 cents! Isn’t pre-union life great? Wait, no, piecework is a miserable existence.

Here’s how the stays work. The ferrules are brazed into each head, and the rods thread into them. Four total, spaced roughly evenly around the head. This should be a very strong design!

At this point, you might be wondering about why the stays are copper, instead of brass like everything else. This is open to debate, and the original article by D.E. Johnson doesn’t say. The general belief about this sort of thing is that copper is safe for steam, and yellow brass is less-so because of dezincification. The theory goes that steam can leech zinc out of yellow brass, leaving the fitting porous and weak, and thus a potential failure point.

This is one of those things that is technically true, but irrelevant at small model scales. Yes, for a larger steam engine running north of, say, 150psi, there are regulations governing what types of materials to use in pipes and fittings. You probably shouldn’t make the whole boiler out of brass at any scale, although people do. There are some brass fittings in this design that are in contact with steam, so it could be a point of concern. However, the flip side is that using brass fittings in small low-pressure boilers is common practice, and model boilers are not murdering people by the thousands. For further antidote to any imminent concern-trolling, the design here is by a man with plenty of boiler making experience, and published in a reputable magazine all about making steam boilers. If this thing was a death trap, we’d know about it. Finally, note that dezincification mainly happens when using mineralized water in the boiler, and I’ll be running only distilled in this one (mainly to reduce scaling problems).

So, is dezincification of yellow brass in a steam environment a real problem? Technically yes. For us, no. If you’re building a big high pressure boiler, stick to bronze fittings and cast iron pipe. If you’re building a fun little one, relax and get on with your life, already.

Okay, back to our heads! Each head serves an additional important purpose. One holds the electric heating element, and the other holds the thermoswitch that controls it. They are both immersion devices, and we need mounting bosses for each. I opted to buy suitable bronze pipe fittings for this, since it was easier than trying to make them. The heating element in particular uses a very large NPT thread which I didn’t want to attempt to make myself.

For the heating element, I bought an adapter fitting from one pipe thread type to another. The “other” didn’t matter, but the inner thread matches my heating element. Bronze is pretty expensive, so buying a commercial casting like this saves a lot of material and thus hard-earned Patreon farthings.

Here’s the large bronze casting for the heating element. It’s functional, but a pretty dreadful casting. You get what you pay for, I guess. I opted to clean it up a bit. I faced the front, to start.

I then flipped it around and turned the outer threads off, since we don’t need them.

I then cut it down to an appropriate length, and we have our mounting boss!

The poor quality of this fitting would come back to haunt me later, though. I had difficulty getting these threads to seal. More on that in a later article. Anyways, I repeated this process with a much smaller bronze casting for the thermoswitch.

You might be asking why I have two of these? The first one was of such poor quality that the thermoswitch wouldn’t even thread into it. The threads weren’t even salvageable in a way that I would trust them to seal, so I ordered a second one. The junked one will find new life as something else someday. The junk pile taketh and the junk pile provideth.

Note that all of the small head fittings were turned to a couple thousandths over size for the holes in the heads. I then used a tapered hand reamer to open up each hole slowly until the ferrule/boss/etc was a very close fit. This should help make brazing cleaner and easier later.

Because each ferrule is handed fitted to its respective location, I labelled everything to keep track. Note that the copper is still blackened from the annealing needed by the roll-forming operation. There’s little point in cleaning it up until later, since it’s going to keep getting dirty.

With the two large bosses made, it was time to make holes in the heads for them. The heater element boss is particularly interesting, because it’s much larger than any drill bit I have. This would be a good operation for a boring head in a milling machine, but I also possess neither of those. When all you have is a hammer, you view every problem like a nail. When all you have is a lathe, everything starts to look like a faceplate operation. You’ll see what I mean shortly.

I started by laying out where I wanted the big hole to be. I made a couple of attempts at it, then punched the center when I was happy.

The only way I have to make a large hole is the boring bar on the lathe, so we needed a setup for that. Not really planning ahead at this point, I started with the four-jaw chuck. First we need to make a hole big enough for the boring bar to get started.

I clamped the head gently in the four-jaw chuck (to avoid damaging the rolled edges), and dialed it in using a dead-center on the punch mark made earlier.

I then center-drilled and drilled up to my largest bit size. I worked up in drill size, since the head is clamped lightly to avoid deforming it.

Now we’re ready for the boring bar. It was at this point that I realized I couldn’t go any further with this setup. There wasn’t room to clear the jaws with the boring bar– the hole was too big. There also wasn’t room to get sacrificial material between the workpiece and the jaws, so it was time for the faceplate.

The setup I came up with involves sacrificial aluminum strips threaded to accept short mounting screws. The strips are mounted to the faceplate with hardware smaller than the faceplate slots, which allows me to adjust the piece to get it centered.

I put a dial indicator on the inside edge of the hole I drilled in order to get it back on the same center it had in the four-jaw set up from the previous operation.

This setup was very time consuming, as I had to gently tap the piece around until it was dialed in. I didn’t have the luxury of any jaws to adjust, and the directions of motion available here are not orthogonal. All the mounting plates are at weird angles, so I had to learn how tapping each one affected the run out, then use that knowledge to dial it in. It was tedious, but I only had to do it once! This would have been immensely easier if I had started with the faceplate, since I wouldn’t be trying to indicate in an existing hole (with a gap in it, no less). However, it goes to show that with some sweat and ingenuity (in that order), you can recover almost any situation in the machine shop.

The setup was tricky, but the end result was brilliant! The boring bar worked like a champ and the large hole is exactly where I wanted it.

I used the telescoping gage to get the diameter half a thousandth larger than the boss I had turned from the crappy casting. Just enough for a snug slip fit.

A perfect fit! Note that the boss is partly covering two of the holes for the stay ferrules. I filed down the sides of this piece for clearance. It doesn’t need to remain a perfect hexagon. As long as there are flat sides, we can grip it with a wrench as needed.

With that, our heads are ready for assembly! We’re getting perilously close to being able to assemble this boiler now. We’ll be making steam (maybe) before you know it, so stay tuned!

One last thing- Blondihacks is now on Instagram! Follow me there for sneak peak photos of upcoming projects. You can find that link (as well as Twitter) any time at the top of the site.

A boiler head is the “end cap” of the pressure vessel. Real steam locomotive boilers are made by rolling a large piece of stock into a tube, and sealing the seam (with rivets, welds, or other methods). The ends are then closed off by attaching round caps to form a closed cylinder. These caps are called “heads”, perhaps because one of them is at the “head” of the boiler in the locomotive as seen from the position of the engineer. The heads are generally rounded, so as to avoid a sharp corner around the end profile of the cylinder. Sharp corners concentrate pressure, and become weak points in the structure. This is the same reason the air tank on your compressor is shaped like a pill capsule.

We’re going to make our boiler heads from 16 gauge flat copper stock, which is close to the same thickness as the water pipe we used for the main body. We can’t go thicker than that for reasons that will become clear shortly.

Much like the big girl boilers, we want to achieve the rounded edges our on heads. Truth be told, since our boiler’s operating pressure is only in the neighborhood of 50psi, this is probably more aesthetic than anything. It’s safe to say this boiler is vastly overbuilt for the job it is doing.

Here’s roughly what we’re going for. These are D.E. Johnson’s drawings of his heads, and I used this as a rough guide for making mine.

A traditional way to made rounded caps like this would be hammer-forming. You make a form out of steel, hardwood, the skulls of small children, whatever is handy. You then hammer the copper against that form until you get the shape you want. This is fine as far as it goes, but there’s a much cooler way we can do this- roll forming on the lathe. This is an industrial process that is actually pretty easy to replicate at home, to some degree.

To start with, we need a pretty fancy piece of tooling. Definitely the fanciest we’ve made so far on this project. The tooling is a forming plate (similar to what you’d use for hammer-forming) attached to a mandrel that we can chuck in the lathe. The front of the form is threaded to hold a clamping plate. This holds our workpiece. We then make a roller that mounts on the tool post to do the forming. Let’s get going on the form tooling.

The junk pile produced this beautiful slug of 6061 aluminum, a whopping six inches in diameter. This is larger than we need, but it’s what’s on hand.

To start with, I need to cut a slice a bit larger than we’ll need. The thickness isn’t super critical here, as long as it’s deeper than the rolled heads will end up being.

All hail the automatic horizontal bandsaw. This is one of those jobs that I just don’t know how you would do otherwise. This cut took about 30 minutes, so imagine doing that by hand. You could torch-cut it, I suppose, but it would make a colossal mess and waste a lot of the material. This cut was lubricated periodically with WD-40, which works great on aluminum.

With our rough piece made, we can get all precise up in here.

The rough slug was faced on one side, then flipped and seated against the chuck jaws. Since that first side is machined, we know that facing the other side while seated against the chuck jaws will give us two parallel surfaces.

Power cross-feed was super helpful for these operations. Six inches is a lot of diameter to feed by hand on a small lathe. Power feed is also helpful in achieving a good surface finish, which is important. Any imperfections in this surface can be transferred to the copper.

The center of the piece was center-drilled, drilled, and reamed to a precise dimension. The mandrel will be a press-fit, so this dimension is critical.

An interesting aside, concentricity is not critical at this stage, because the mandrel will establish the center axis of the entire tool, and this piece will be turned to match it later on. Efficient machine shop work is all about knowing which dimensions are critical, and where in the order of operations those dimensions will be coming from.

A mandrel is turned to an arbitrary dimension (it just needs to be true and with no run-out). A short section on the end is turned to one thou larger than the hole we reamed in the plate. The end is center-drilled for support, but this will also be our center for later.

Here we can see how things will fit together. Note the plate was chamfered to ease the press-fit, and ensure it seats against the shoulder. Inside shoulders always have a tiny fillet, no matter how sharp your tool is. To get a tight fit, you have to undercut the shoulder, or fillet the mating piece.

To do the actual pressing, the right tool would be an arbor press. Since I don’t have the right tool, I’m going to use the wrong one– my bench vise. This works as long as the press isn’t too demanding. We’re only one thou over here, so it’s manageable. The risk is breaking the acme-threaded lead-screw in the vise. Sooner or later that will happen if you abuse vises in this way. But not today.

I also used some Loctite 603 on the joint to make sure it holds forever. It pressed together like butter and will be very strong indeed.

Here’s our finished mandrel, pressed into place. So far so good!

Next we need to turn down the diameter of the plate, which will also get it perfectly concentric with our mandrel. To do this, it’s time for the four-jaw chuck. As soon as the mandrel was removed from the three-jaw after turning it, concentricity was lost. The four-jaw is how we can get it back.

The mandrel is indicated in to as close to zero run-out as we can get it, and we’re ready to turn the disk. Note the center hole on the mandrel now becomes our live-center support for this operation.

Our disk is almost two full inches larger than we need it to be, so we have a lot of chips to make. Turning aluminum is one of my least favorite things to do. It’s very difficult to get it to make decent chips. Plenty of WD-40 lubricant and pouring on the speed seems to help, but stringy rats’ nests of chips that pile up on the chuck is hard to avoid.

Dear aluminum, I hate you. Love, Quinn.

With the diameter turned down, we need to form a large fillet that will give the boiler heads the desired shape. To do that, I made a large-radius form tool.

Here’s an easy way to get a quarter-round form tool- simply choose a Dremel sanding drum (80 grit) of the desired size, and hold it at an angle. This gives the needed side and back rake, while leaving the top profile we want.

Here’s the form tool in action. Note that you could also do this by hand with a file. Form tools are fun though!

After grinding the profile with the Dremel, you can grind a top rake in the usual way, if needed. I decided to give it a try with zero top rake, which is the opposite of recommendations for aluminum. This worked surprisingly well, despite aluminum usually requiring a lot of top rake.

The final operation on this setup is to drill and ream the center to take a piece of drill rod. This serves as the registration pin for all the operations that will be done with this tool.

Here’s how it looks with our alignment pin inserted.

Next we need to make a clamping plate for the front face of the tool. For this I grabbed a chunk of three inch steel off the junk pile and faced both sides of it.

The center was marked, and five other holes were laid out. These holes match five that will be in the final boiler heads, and thus can be multipurpose. They will be used for clamping screws, alignment pins, and as drill guides.

This layout was really tricky, since there are no fixed reference points and the holes are in a trapezoidal pattern. I did it all with a simple compass and a lot of math. Sometimes the old ways are still the best ways!

The drill press was used to drill and ream the center hole to match the drill rod registration pin.

A quick test fit shows we’re in business!

To guarantee all the mounting holes line up perfectly, I match-drilled everything (rather than trying to do that tricky layout a second time and hope for an identical result).

After the first hole was made, I dropped a scrap pin in there to keep everything aligned while the rest of the holes were drilled.

Lastly, the holes in the base plate were tapped to accept the clamping plate mounting screws. I used my shop-made tap follower in the drill press, since it was already set up.

This tool turned out really really pretty, but not by intention. When you work precisely, beauty just happens in the machine shop.

With the base tool and the clamping plate done, all we need is the roller tool. For this, the junk pile produced a chunk of brass and an old roller blade wheel. Discarded roller blades are a great source of high quality bearings. They’re typically ABEC-5, and the “tire” part of the wheel is consumable, so the bearings are usually still good in worn-out wheels.

I reused the bushing from the wheel to clamp the bearing to my brass holder. It’s already the perfect length to prevent the hardware from clamping against the outer bearing race.

Here’s the assembled roller tool. This goes into a tool holder on the quick-change toolpost, and Bob’s your uncle.

Okay, the tooling is done! Now we get to make some boiler heads!

I cut the copper stock to an octagonal (ish) shape on the bandsaw, then drilled the registration hole in the middle.

With the registration pin keeping things aligned, I then used the clamping plate as a drill guide for the rest of the holes.

With the holes drilled, the copper is then affixed to the tool with the clamping plate.

With the tooling chucked in the lathe, we’re ready to get some hot boiler-head action going!

I started by turning the copper down to the right dimension. This is a bit tricky to calculate, because you need to account for the radius of the bend that will be created. There are online calculators that can help with this.

With the diameter set, we’re ready to start forming! Copper can be tricky to machine, but I find the same tool bit profiles used for aluminum work pretty well.

The actual forming process needs to be done slowly and carefully. A very low RPM is used, and the roller is set at just ten degrees off the face. As the roller touches the copper, the material will gently fold over against the form. It’s critical not to leave the roller touching any longer than necessary, because copper work-hardens very easily. If the copper hardens, you have to remove it and anneal it with a torch to get it soft again. This will need to happen anyway, two or three times during the process.

If you get greedy on the angle, the edge of the roller will dig in and scar up the surface, so be patient and go ten degrees at a time. Use the compound to feed the roller tool into the work, and keep the carriage and cross-slide firmly locked for rigidity.

Here’s a video of one 10 degree roll operation.

Every third or fourth pass, the piece is removed from the lathe, heated to cherry red, and allowed to cool slowly. This makes it soft again, and we can go another three passes or so.

I stopped and annealed each head four or five times. Once the copper is fully seated against the curved form, we’re done.

Here’s the final result of rolling one head. The markings you see buff off easily.

This fixture may see further life later as a small faceplate, or I may make more heads with it. That’s all for now! Roll forming sheet metal on the lathe is easy and fun. Making the tooling is a great exercise also, and the end result is undeniably pleasing. I hope you agree!

Last time we made a bunch of straightforward plumbing fittings. We have more fittings to make, however, and we’re getting to some very interesting ones. Next up is the steam dome. What’s a “steam dome”, you may ask? Well, ever wondered what those bumps are on the tops of steam locomotives? At least one of them will be a steam dome. There may also be a sand dome, and some domes are just covers over equipment, but a steam dome there will be.

Boilers make steam by boiling water- every schoolchild knows that. However, steam comes in many different grades. Broadly, steam is divided into “wet” and “dry”. This is basically a measure of how much water vapor is suspended in the steam. Steam engines need to run on dry steam, because suspended water droplets would collect in cylinders and valve gear, gumming up the works. Since water isn’t compressible, this can in fact be fatal to pistons and rods. Too much water in the cylinders leads to hydrolock, which is a very efficient way to destroy piston connecting rods.

Dry steam is also generally invisible (or very hard to see) because the water droplets in wet steam are what you can actually see. This makes live steam (aka dry steam) very dangerous. It’s much hotter than wet steam and very hard to see. Industrial steam cleaners, for example, produce live steam, and are a super good way to have a real bad day.

The purpose of the steam dome is to isolate the desirable dry steam. At its most basic, it’s just a high spot in the boiler. The dry steam rises (because it’s the hottest) and collects at the highest point. The steam dome takes advantage of this to concentrate the dry steam and funnel it to the engine. This is passive steam separation, but there are active methods as well. There are centrifugal steam separators, for example, that leverage the mass difference between wet and dry steam. Our steam dome is a very simple one, consisting only of a high spot in the boiler, and some small holes to help prevent water from splashing up in there.

Here is the drawing for the steam dome as presented by D.E. Johnson. It consists of a brass dome turned from solid stock, with a copper stay down the center of it. Mr. Johnson makes the point that the braze joint is in tension here, which is not ideal. Silver solder is strong in shear. The copper stay down the center reinforces the dome’s joint with the boiler.

The steam dome is an interesting part to make on the lathe. It starts with a large piece of brass stock, turned to 1.5 inches.

As is tradition, we start by facing the end. Power cross-feed is pretty nice here.

The outside is then turned to the largest diameter of the dome’s shape, which is the 1.5″ flange at the bottom.

The top of the dome has a very generous filet on it, which gives it a dome-y sort of look. This is primarily decorative, I think, since a blocky cylinder would feel unfinished. There are a couple of ways to create this. Brass turns fairly easily, so it is possible to shape it with a hand-held tool, similar to wood turning. I’m not personally a fan of this, since it doesn’t feel very safe to me. Another approach is make a form tool.

Form tools for brass are easy to make, because the ideal top rake angle for toolbits on brass is zero. This means we only need to make a profile in one plane, with a bit of side rake. For curves, an easy way to do this is Dremel sanding drums. They come in a lot of diameters, so I simply choose one that is the exact diameter I need. By grinding away one corner of the tool bit, with the drum held at a slight angle, we get a perfect form tool with side-rake in one operation.

Here you can see the form tool made with a Dremel sanding drum, and the resulting curve achieved on the brass stock,

Form tools are not used very often on metal lathes because the tool pressure is very high. You need tremendous rigidity to keep them from chattering and making a mess of the part. There’s a reason lathes are primarily single-point cutting tools- to minimize tool pressure. Form tools go against that, and on a small lathe like this you can’t get away with much in this area. Brass is easy enough, though.

With the outer shape achieved, it was time to make this into a dome (instead of… a stump?). I parted off the piece and flipped it around. To keep our concentricity with our existing turned areas, I used the four-jaw chuck and dialed it in with the piece flipped.

To prepare for hollowing out the dome, I drilled all the way through with the tap drill size for the stay, then cored it out with a 1/2″ drill to the depth of the dome interior.

Next it was on to one of my favorite lathe activities- boring! Boring bars are neat things, and it’s cool to be able to make very large holes to very precise dimensions without drills.

I used a dial indicator to set the depth of the dome interior (calculated from the drawing to leave the correct wall thickness.

Here’s the dome all bored out. I’m very pleased with this result!

As you may recall from the drawings, there’s a stay down the middle of the boiler. This stay is made from copper. I’m not sure why, but that’s what the plans called for, and I’m trusting that Mr. Johnson knows a lot more about steam boilers than I do. This stay has a 1/4-20 thread on the end, so we need to tap the dome for it.

Since we’re already on center with that hole, I tapped it in-situ with my trusty tap follower chucked in the tail stock.

The next operation is to make holes in the sides of the dome. One hole is the steam output. This is the entire raison d’être of the boiler! The nice dry steam collected in the dome is pushed out through a valve in the side of the dome, to be delivered to the engine. Once at the engine, that steam will drive the pistons which turn the flywheels which power the looms which make you wealthy, all while efficiently oppressing your non-unionized factory labor. It’s the Victorian dream!

To lay out the cross holes, I used the surface plate. There are lots of ways to do any particular layout task, but the surface plate seemed easiest for this.

For the actual drilling, it’s over to the drill press. This operation could be done in the lathe, but the setup would been a lot of work. We don’t need ultimate precision here, because the bosses that go in these holes will be made to fit. Thus, the drill press will suffice. Nevertheless, setup was done carefully, and the part was center punched, center drilled, drilled 1/64th under, then reamed to final dimension. A cheap drill press can do reasonably precision work with careful technique.

Here’s a handy machinist trick- a pair of V-blocks in the vise make holding large round pieces a breeze.

Now here comes the really interesting operation on this part. The dome needs to fit tightly against the top of the shell, which is a cylinder. Thus, we need to remove a curved section of material from the bottom of the dome of the same radius as the boiler itself. Not only that, it has to be a very good fit, because it will be brazed in place. Brazing, as we know, is not great at filling gaps. You need well-fitted parts. A milling machine would be a great way to cut this curve, but Blondihacks Labs is presently absent one of those. The part could be set up sideways on the faceplate of the lathe, at the right distance-from-center to bore the needed radius. I very nearly did this, but it was going to be an extremely complex setup, probably requiring some fixturing to be made. Instead, I decided to go low-tech: hand filing and lapping. Let’s see how that went.

For starters, I scribed the outline of the curve I needed. I did this by carefully arranging the boiler shell above the dome and tracing it. This worked surprisingly well.

Filing a part to a specific shape takes a lot of skill, and I do not have much experience with it. I decided to practice on some scrap first to see if I could get the technique down before risking this part that I have several hours of machine work into already.

With a combination of round and half-round files, I was able to rough in the shape.

To get the final curve, I felt that lapping it in would the safest and most precise. To do that, I would need something the exact shape of the boiler shell. Well, I have the boiler shell itself! Why not use it to lap in its own steam dome? Let’s test this idea…

I put a layer of sandpaper on the boiler and set it up in the holding jig. Doing it by hand like this was working, but it was very slow and very labour-intensive. What I needed was a way to move that sandpaper automatically. Like… if it were… spinning…

With the sandpaper overlapping in the direction of the lathe’s spin, and cardboard to protect the ways from all the nasty sanding grit flying everywhere, I had my power-lapping setup. This actually worked really well.

With the technique determined, I held my breath and tried it on the real thing.

Again, the dome was first roughed-in close to the layout line with a half-round file.

I used the same lapping setup on the real dome, working it until I reached the layout line.

I was very pleasantly surprised at how well this fit. I really could not have asked for much better on my first attempt.

Here’s a closeup, and you can see how nice that fit is. If you could see my face in this photo, you would see my shocked face. Because I am shocked. And it shows on my face.

On the other side, there is a slight defect where I got carried away with the file. There’s no Control-Z in the real world, so you have to be careful.

I feel that I should be able to fill that little gap in the upper left with silver solder. I’m willing to gamble on it, rather than making another part now. I could try to lap it further, but I don’t think I have enough material left in the shoulder to go any deeper.

The last piece of the steam dome puzzle is the outlet valve. We need somewhere to connect that. I won’t be making the valves themselves- they were purchased from PM Research. Instead, I just need to make a boss to which I can attach the valve. I’ll also be making a 1/8″ NPT boss for the other side of the dome and plugging it. This is for future expansion, should I ever wish to draw out live steam for a secondary accessory or some other purpose (such as scalding my enemies).

Starting with hex bar stock, I laid out all the diameter changes. We need a boss that will fit snugly in the steam dome on one end, a ¼-40 thread on the other end, and a hex section for a wrench in the middle.

The smooth section will be brazed into the steam dome, and was made via two plunge cuts to the same cross-slide dial reading from a parting tool. This works well as long as you back out far enough to remove all backlash in the cross-slide when coming back in for the second cut. The same dial reading will get you to the same surface. As long as you are mindful of backlash, the dials are a very reliable local coordinate system.

Here are the completed steam dome parts, ready for installation.

That about does it for our major fittings, and also for this post.

Here’s a family photo of the more interesting fittings we needed to make. Not shown are a bunch more 1/8″ NPT ports, a whole bunch of boiler stays, and other boring parts.

That’ll do it for now. Pretty soon we’ll be ready to start assembling this beast, but we have two more major parts to make before then. Stay tuned for more hot boiler action.

I used to think a boiler was a big metal shell that you pressurize. That’s a good description of an air tank. However, a steam boiler is really a system that has the pressure vessel as one part of it; but there is so much more. A steam boiler is more like a fancy way to store a hundred fittings. Because holy cow are there a lot of fittings needed to make a functioning boiler system. You can buy most of these in the plumbing aisle of your local website, but I decided it would be much more fun to make them all from scratch. That was a really great idea until around fitting number 86. Then it got old. Okay, I’m hyperbolizing here, but that’s my prerogative as the sole proprietor of this blog.

I really like working with brass in the lathe, so this was a great opportunity to do a lot of it. 360 free machining brass is really easy to get a beautiful finish on, and you don’t need cutting oil or coolant for most operations. It also makes very nice chips, so cleanup is a breeze. Surface speeds are generally low, so the lathe is running quietly, which I enjoy. It’s basically the opposite of aluminum in every way, which is why I really hate machining aluminum.

To make plumbing fittings, an easy route is to start with hex bar stock of the size that you want the “wrench” part to be. The rest of the fitting is machined down from there. Pretty much every fitting here will have a hexagonal section, because I want to be able to use two wrenches at each connection to avoid stressing braze joints and such.

To get my feet wet (pardon the pun), I decided to start with the fill plug at the top of the boiler. This is super useful, since at the moment all water is outside my boiler and at some point a portion of the earth’s water needs to be inside it.

Starting with some largish hex stock, a shoulder was turned down and a thread cut with my shop made tailstock die holder. I didn’t do a blog post on that tool, but if you’d like me to, let me know in the comments.

Now for the bushing part of the filler. This is a straightforward part as well. Parts like this are where you really appreciate seeing your own skills in the machine shop develop. When I first started, a part like this would have taken me a couple of hours. I can now knock out a basic plumbing fitting in a few minutes. You gradually learn all the million little work habits that slow you down, and you learn which parts of the setup are important and which are not. The more you learn exactly where to apply precision (and thus time), the quicker you get.

The bushing (or boss, if you like) has a round part that goes inside the boiler shell. This is the surface that will be brazed. The hex area is to put a wrench on for tightening the plug without stressing the braze joint.

This hole was bored, since the tap hole size for this thread is larger than my biggest drill. I don’t know why I photographed it with the boring bar this way after I had obviously already tapped the threads, except that I really like that boring bar. Okay, I guess I do know why I photographed it this way.

Here’s the completed set, ready to go in the boiler. Since this is a straight thread, it will have an O-ring on it to seal against the pressure.

The next set of fittings to make are considerably more complex. These are for the water level gauge. It’s super important that the water level in a boiler never drop too low. In the case of this boiler, it can’t drop below the level of the heating element. The heater is designed to be fully immersed, and it will burn itself out if exposed to air while powered. The traditional way to monitor water level in a boiler is with a sight glass. In this case, it’s a glass tube the same height as the shell, which is plumbed in to the top and bottom. This tube is pressurized with everything else, so it needs to be pretty sturdy.

Here’s how the water gauge is installed. Traditionally, this would be plumbed in to one of the heads on the end, but on this design there isn’t room.

The water gauge itself was ordered from PM Research, a supplier of scale steam components. I considered making this from scratch, but the glass has to be borosilicate to cope with the temperature and pressure changes, and that stuff is really expensive. It was actually about the same price to buy the whole gauge from PM Research. Gauge in hand, I only needed to make fittings to connect to my boiler.

Each half (top and bottom) needs a mounting boss, an elbow, and an extension pipe to reach out to where the gauge sits.

The mounting boss is turned from hex bar stock, sized for a 1/8NPT pipe thread. I got to make this twice, because the first time I made it reversed, forgetting that pipe threads have to be tapped from the same side the mating piece will be entering from. Whoops!

This is a good moment to pause and talk about pipe threads. In North America we have the NPT, or National Pipe Thread standard. What’s interesting about this is that the threads are tapered. This makes them self-sealing against liquid and gas pressures, because as you tighten them, the threads wedge together as much as needed to stop leaks. With a normal straight thread, the tolerances of the thread cutting mean there’s a path all the way through the fitting where gas can escape. A common misconception is that the hole (or pipe) for a pipe thread is itself tapered. In fact, the stock is straight. Only the threads themselves are tapered. A diagram will help.

As you can see, the threads get shallower as you get deeper into the hole. The stock is straight, but thread form is cut tapered.

This “tapered thread in straight stock” profile makes these threads difficult to cut. Pipe thread taps are always really beefy for this reason. For proper sealing, you need at least double the nominal dimension of overlap (in this case 1/4″ for 1/8″NPT thread) so you have to make sure to cut deep enough. In my experience, “deep enough” is usually a bit past where you’re really having trouble making progress with the tap and/or you’re starting to get concerned about breaking it. It helps to mark the needed depth on the tap so you know before you start. I opted to standardize almost every fitting on this boiler at 1/8″NPT. It feels like a nice size for this application.

Let me pause to head off the comments, here- pipe threads are actually a really complicated topic that I have oversimplified for brevity. There are different forms for low-pressure, high-pressure, structural, dry-seal, putty-seal, and all sorts of others. Some pipe threads are straight threads cut into tapered stock. However, the basic NPT form I describe here is mostly what people mean when discussing pipe threads.

The boss connects to an elbow, and this is where I found out I had made it backwards.

For these elbows, I decided to buy them. They would have been easy enough to make, but some reason I decided to make them with my Amex this time. This form of elbow is called a “street ell” on the streets. A street elbow has one male and one female end, which is handy for making extensions like we’re doing here.

The last part of the water gauge system is the extension pipe, and this is the most interesting fitting. I decided to make it look like a pipe with a narrow hexagonal section in it for wrenching on. One end is 1/8″NPT to mate with the street elbow, and the other end mates with the water gauge.

Starting with our old friend the hex bar, I cut 1/8″NPT thread on one end. I also faced and center-drilled to prepare for the next operation.

The bar was then supported by the tailstock, and I made plunge cuts with a wide parting tool to create shoulders at the transition areas. The hex area on the right will remain hexagonal, the middle will be turned down to the “pipe” diameter, and the left end will be turned down to the thread diameter at that end.

The middle portion was then turned down with a radiused tool to get a nice finish. I calculated this diameter to get a nice wall thickness, given the 1/8″ ID of the whole fitting.

Finally, the leftmost area was turned down for the small thread on that end. This was parted off and flipped around for threading.

Threading the small end got interesting, because it’s not a typical thread. The water gauge is a model engineering part, so the thread is from the class of weird little threads that model engineers have come up with. In this case, we need a ¼-40 thread. That’s a teeny thread that has a corresponding teeny die to cut it. I cut all my threads using a tailstock die holder that I made as an afternoon project. It works great, but it is sized for 1″ round dies (the most common size). I could only find ¼-40 thread dies in the smaller 13/16″ size.

As I’ve often said, the great thing about machine tools is that any time you need a new tool, you can make it. In this case, I needed an adapter for 13/16″ thread dies to go in my 1″ holder. Let’s make that!

A piece of 12L14 steel scrap from the junk pile gave its life for this. I turned the outside diameter to a few ten-thousandths below 1″ to be a snug slip fit in the holder. Precision is important here, because we’re adding layers to the tool. Each layer is a chance to accumulate error in the work produced by the tool.

This is a nice simple lesson in accumulated error. If all the surfaces on this adapter aren’t as flat, true, and square as we can get them, the die held in the adapter will introduce error to the work that the original tool did not have. Imagine if Lego bricks were made haphazardly, for example. Two walls of twenty bricks would come out a different height, and you couldn’t put a roof piece across the top of them. That’s accumulated precision error. Lego bricks are made to an astonishingly level of precision, not least for this reason. Accumulated error in any dimension would ruin the whole system in short order.

The interior was drilled, then an inside shoulder was bored to fit the 13/16″ die.

There was some careful math to get the adapter seated in just the right place. The 13/16″ dies are thinner, but the same setscrews used to retain the 1″ dies need to pass through the adapter and land dead center on the thinner dies. The holes in the adapter are drilled clearance size for the setscrews so they don’t interfere with the clamping.

With that snazzy new tool made, I was able to finish the extension pipes for the water gauge.

The adapter worked perfectly for cutting the little ¼-40 threads.

All of that x2, and we have our water gauge extension pipes.

The last fitting to be made in this batch is an elbow for the bottom of the boiler. This is to attach the blowdown valve. Boilers boil water (no, really!) and boiling water pulls minerals and other impurities out of it. These impurities collect inside the boiler and reduce the efficiency of it. You want to clean these out periodically.

One of the interesting things about cars is that they manage to do every job in the car using gasoline. Windows move by electric motors powered by an alternator driven by a belt off the crankshaft. Thus gasoline moves your windows up and down. The typical car heater works by piping hot engine coolant through a radiator core, and this coolant was heated by the engine’s combustion, which comes from gasoline. Thus your heater is powered by gasoline. Yes, there are exceptions, such as old air-cooled Volkswagens burning gasoline for heat, and using spare tire pressure for the windshield wiper. But in general, you use the power you have on board.

Steam locomotives and stationary boilers are the same- they have creative ways to use steam to do every job they need. In the case of cleaning impurities, we have the blowdown valve. Since the impurities are heavier than water, they settle to the bottom. While the boiler is under steam, we can crack this valve at the bottom of the tank and the steam pressure will blow all the impurities out the bottom (along with a bunch of scalding water- steam engines are not for amateurs). Note that there are also surface blowdown valves on some boilers, because the water/steam interface is where a lot of dissolved impurities collect during operation. For this basic little boiler, a bottom blowdown is all we need. The bottom blowdown valve is also the drain when we’re done playing.

Since my boiler doesn’t have a lot of clearance under it, I need an elbow to get the blowdown valve out to where it can be reached. I decided to make an elbow fitting that can be brazed directly into the shell.

Starting with a large piece of hex bar, I turned the “boss” portion that will go in the tank.

The boss was drilled to where the centerline of the final elbow will be. This piece was then parted off so we can drill the other angle.

Next I needed to flip it 90° so I could drill the other opening. This was a job for the four-jaw chuck.

Here’s an old machinist’s trick. The dead center is held between the live center and a center punch on the part where the hole needs to go. A dial indicator is then used to dial in the dead center. That will put our hole on the center line of the lathe for drilling and tapping. Note the wooden board to catch the dead center if it slips out. It could put a nasty ding in the ways.

Result! This hole is perfectly centered, and is subsequently tapped for the blowdown valve.

As I make each of these fittings, I give them a little shine with some 400 and 800 grit emery paper. It makes them look all spiffy.

I also made a bunch of 1/8″NPT braze-in bosses for other random purposes, such as the pressure relief valve. I made a couple of extras that will be mounted and plugged, for future expansion. Adding a fitting later if I decide I want other boiler accessories (feed pump, water injector, condenser, superheater, etc) will be a whole lot easier if I don’t have to dismantle the boiler and drill new holes in it.

We’re not done with the fittings yet, but we have all the monkey-work ones done. There are still some really interesting and special bits to be made, so stay tuned for that!

]]>http://quinndunki.com/blondihacks/?feed=rss2&p=39848Renovation!http://quinndunki.com/blondihacks/?p=3965
http://quinndunki.com/blondihacks/?p=3965#commentsTue, 01 May 2018 03:56:03 +0000http://quinndunki.com/blondihacks/?p=3965A whole new look and location for this old blog.

I know, right? It’s crazy in here all of a sudden. Well, here’s the deal. The old Greyzed WordPress theme has served me very well for nearly a decade, but it hasn’t been officially supported for a long time. That has made maintenance and upgrades around here increasingly difficult. As WordPress continues to be updated, the theme was developing more and more problems. In any case, while I dug the art style, there were always things I didn’t like about it.

It was time for a change, but it turns out that in the intervening years, the entire web went to a “modern” style, and so went every single freaking WordPress theme. “Modern”, of course, means giant white screens with rectangles of color here and there, and more Helvetica than you shake a serif at. I’m not a rectangles-and-helvetica person, and frankly I’m weary of it being absolutely everywhere. That meant I needed to get my hands dirty, which is why it has been a little quiet around here.

I’ve spent the past few weeks learning way more than I ever wanted to about WordPress in order to CSS and PHP my way from a standard theme into something that says “Blondihacks”. I wanted to keep suggestions of the old look, while making it easier on the eyes, easier to navigate, and more friendly. You’ll note that comments are now available right on the front page article. No more clicking around to find them. The site is also now responsive on mobile, although it gets very “tall” as WordPress sites do on phones. “Responsive” in WordPress means “stack everything up”, as it turns out. There’s an old joke that says there are two hard problems in computer science- cache invalidation, and centering something in CSS. I can now vouch for that firsthand. I feel like a goram WordPress superhero now, which I never wanted to be. Anyway, if you find broken links, missing images, etc, please let me know. I think the migration went well, but it was a big job.

That’s not all, though! In addition to the familiar RSS button at the top, you’ll also find a Twitter button and an email address. I want it to be easier for readers to reach me.

But wait- I’ve totally buried the lede here. The site now has its very own domain! That’s right, you are now officially at:

Isn’t that nice? Seven years, and I finally got around to getting this thing off my personal website. That means you should update your links and bookmarks, because the old URL is going away at some undisclosed future time. If you use RSS, make sure to click the RSS button at the top to update your feed. [UPDATE: Well, not really. GoDaddy’s domain masking turns out to be super broken, so the new domain simply forwards to the old location for now. I’ll warn everyone if and when the old host goes away, so don’t worry about your bookmarks and such for now]

There are more big changes coming down the line. I’m working on some exclusive perks for Patreon subscribers, so those of you who had the faith to invest in me will be seeing some awesome new stuff that nobody else gets. Stay tuned for that.

As always, Patrons pay per post, and that does not include frilly administrative posts like this one. You only pay for the real content, and only when I get off my ass to produce it! Thanks as always, Patrons. You gals and guys are the swellest.

I hope you enjoy the new look, and watch for more regular content soon!

Yes, change is scary, but follow the lead of Sprocket H.G. Shopcat and let it all hang out. You’ll feel better!

With the boiler shell basically ready to work on, it was time to finally get down to making some parts. The legs seemed like a good place to start, because they are pretty straightforward parts and make for a good way to ease into this hefty project. Little did I know the legs would be such an odyssey! Design iterations and failures abound in this seemingly simple job, so buckle up and witness me.

The purpose of the legs is twofold. First, the boiler needs to be off the ground so that the base plate doesn’t get burned (if wood) or rob us of precious heat (if metal). An air gap underneath it acts as an insulator. Second, and more importantly, there needs to be room for fittings on the bottom. Different boiler designs will involve different fittings, but it’s a safe bet there will always be at least a drain valve. Often there is also a blowdown valve (which may be the same as the drain valve) and in our case there’s also part of the sight-glass system for monitoring the water level. In a real stationary boiler, it would be typical for it to be sitting in a built-up cradle made of bricks or cast iron. We’re going make legs because it looks nice and is easy to do (for certain values of “easy”).

The design that D.E. Johnson came up with for these legs looks quite attractive and is straightforward to make, so I started out copying what he did verbatim. His design consists of four legs, each attached by a right-angle bracket that attaches with a ferrule through the side of the boiler shell.

Here is D.E. Johnson’s design. The bracket has a bushing/ferrule inside the boiler that is screwed to a square piece on the outside, to which the leg is attached.

Here’s another look at the legs in Mr. Johnson’s version. Note the square bosses that attach to the boiler.

I deviated a bit from that design straight away, because I didn’t care for the square piece that supports the legs. It felt awkward to me amongst all the round details, so I decided to make all these parts round.

The ferrules inside the boiler are a straightforward turning operation. The outside is turned to an arbitrary dimension (not critical), the shoulder is cut to a depth that matches the thickness of the boiler shell, and the center is drilled and tapped 10-24.

Repeat three more times, and we have our interior pieces.

Next, we need to make the bosses that attach through the shell to those ferrules, and support the legs. As I said earlier, I decided to make them round.

I turned the outside to dimension, and drilled the center for clearance for a 10-24 bolt. I also wanted to counterbore for the head of a cap screw, because this looks very nice. The ideal tool for this would be a counterbore bit, which is designed for the exact job of making a flat bottomed area around the top of a bolt hole. An end mill held in the tailstock chuck would probably also work. Not having any of those things, I used a normal drill bit. You have to calculate the pointy area of the bit and add that to your depth. The shoulder area will be 118° to match the angle of the drill instead of flat, but the bolt head still seats just fine.

Three more of those, and we’re almost done with the leg brackets. However, the legs need a flat part to sit on, so it’s back to the four-jaw chuck.

I laid out a flat area that would match the width of the top of the legs. I used a circle chord-length chart to determine how deep of a cut would result in a flat area with the width I wanted. Machinists have charts for everything. They’re great- doing the math yourself is a source of error and slows you down, so you might as well just look it up.

I then mounted the piece in the four-jaw, making sure it was parallel to the chuck face by running a dial indicator up and down on the cross-slide. Getting a piece like this to run true on the axis of the chuck is a bit tricky- you basically have to dial it in twice, once for each dimension. This is the same technique used to flatten one side of a cylinder for a wobbler engine.

Once flat, I was able to drill and tap 10-24 to receive the stud on the top of the leg. That’s a shop-made spring-loaded tap follower, and it makes jobs like this so much easier. I didn’t blog the making of that tap follower, but if you’d like to see a post on it, let me know.

Repeat three more times and we have our leg brackets! So far so good.

Next up are the legs themselves. These are made from hex stock, mainly for appearance. Hex stock is a lot of fun to work with, and we’ll be doing a lot more of it on this project. You can get very attractive and functional parts by turning down sections of the hex to varying degrees of roundness. You also get attractive effects with chamfering and filleting tools on hexagonal profiles. The one trick with hex stock is that it is difficult to get concentricity with it. If you use the three-jaw chuck, it’s easy to hold, but you’re at the mercy of how true the stock is. Since you have to preserve part of the original surface (otherwise why would you be using hex stock), you lose the ability to “cut below the run-out”. You can set up hex stock in a four-jaw chuck, but dialing it in is really tricky, and two of the jaws are holding on corners, which is awkward and not very rigid. The ideal chuck is an independent six-jaw, but those are hardly common in weekend-warrior machine shops.

The bottom line is, don’t use hex stock for something that needs good concentricity. This is rarely a problem in any case, because if you’re using it, you’re probably making bolts, plumbing fittings, or decorative elements. None of those need crazy high concentricity, typically.

For the legs, the ends are faced and drilled/tapped 10-24.

The center portion of the leg is then turned round to create a nice aesthetic. This turning was done with a 90° chamfering tool that I ground for the purpose, in order to create symmetrical transitions from round to hex at each end.

Note that parting off hex stock can be slightly alarming. It’s a very interrupted cut, and parting blades do not appreciate being treated that way. Very low RPM and gentle feed are the rule until you get deep enough to have a continuous cut. It will sound like a little baby power hammer until then.

Here’s the complete assembly for one leg.

Repeat three more times, and we have all our leg parts!

I was pretty pleased with myself at this point, but a dark cloud was coming. Over the course of many showers and commutes, I was thinking about this leg system and decided it had a critical flaw that I really didn’t like- it requires cutting gratuitous holes in the boiler shell. This is a pressure vessel, and every braze joint that we subject it to is a potential point of failure. I’m also not a particularly good brazer-person. So why would I ask for trouble by using a leg system that demands four extra pointless holes to be made?

I couldn’t bring myself to do it. Instead, I decided to head off the ranch and do something different. All the ideas I had revolved around some sort of clamping-band system that would wrap the boiler and hold it like you might support a pipe in a ceiling. My idea was to have a continuous band over the top, to which one pair of legs attach. The bottom clamp would be two pieces, attached to the legs, but with a gap at the bottom. This gap would be bridged by a bolt that can be tightened to get the clamping action. The bottom clamp would squeeze the boiler upwards into the top clamp, securing it firmly.

I decided to reuse the ferrules that are supposed to go through the boiler, and instead braze them to the bands that wrap around the boiler. This way, the bands would sit flush all the way around, which would be quite attractive, and the legs still screw in as before.

I started by shortening the ferrules I had made to something much thinner, to keep the legs roughly the same width apart.

To make the bands themselves, I fished some 24ga brass sheet off the junk pile. Now, I knew I had a challenge ahead. Sheetmetal work is one of those things where, if you have the right tools, it’s easy and pleasant. If you don’t have the right tools, it’s hell and the result always looks kinda like garbage. I was in the latter camp, but determined to minimize the garbage part. I don’t have a press brake, a shear, seaming pliers, a nibbler, or any of the other things one should use for sheetmetal tasks. I wasn’t about to tool up a whole sheetmetal shop in my laundry room for this one little job though, so let’s see about making due.

I used some card stock to lay out the dimensions for the bands. The hole you see is where the ferrule will be brazed into to tie in the legs.

I know from previous agony that drilling sheetmetal cleanly is a pain in the patouie. The drill deforms the piece, the piece grabs the bit and twists itself up into knots, cats and dogs live together- it’s terrible. Instead, I thought I’d try my hand at making a punch. I’ve never made one before, but the tolerances can be looked up and a punch is ultimately just a round thing with a slightly larger round thing for a die. Lathes are great at making round things, and I have a lathe. Onward!

The junk pile provided this very convenient piece of scrap that is actually already sort of a punch and die. I turned the protrusion to my punch size, then parted it off.

The die part was then faced off and bored to the precise dimension. There are tables that tell you the clearance needed between the punch and die depending on the diameter of the hole and the thickness of material you are punching. In my case, it was 3-5 thousandths.

I double-checked my die bore by fitting the leg bracket into it. This is the hole it needs to make, after all!

Here’s finished the tool. I tested it on some card stock, and it worked great!

Ideally, a punch like this would be made with tool steel, not mild steel like I’ve done here. However, this will only be used on brass, and only needs to survive for eight holes, so I’m not concerned. Okay, enough theorizing. It’s the moment of truth- does it work in actual brass?

The first attempt did not go well. The problem is alignment. Since I don’t have an actual press, I’m trying to do this operation by other means. I tried a hammer and the drill press (not good for the drill press!), but ultimately settled on the bench vise (not great for the vise either). The vise has the clamping force needed, but aligning the tool halves is very difficult.

I worked out a few tricks to get the alignment right, and then it did work pretty well! When the alignment is correct, I was actually surprised how little force is required.

A perfect fit! I was feeling pretty good about this approach, although getting the alignment correct was still difficult, and my success rate without deforming the area from misaligned attempts was not good. An arbor press went on my Festivus list for next year. In the meantime, we’ll continue to improvise.

The next challenge was getting nice one-inch-wide strips cut from my brass stock. Again, the correct tool for this (a shear) makes this a painless task (as long as you keep your fingers out of said shear) and delivers perfect results. I needed another way.

The first thing I tried was the bandsaw. The standard Asian import 4×6 horizontal bandsaw that we all have comes with a terrible little table that lets you set it up as a vertical bandsaw. I’ve used this a few times in a pinch, but it’s not great. In this case, it did cut, but it left a pretty rough edge because the blade I have on there is much too coarse for thin material like this.

The rule of thumb on bandsaw blades is that three teeth should be inside the material during the cut. For 24ga material, that means you need a very fine-toothed blade. This idea was a no-go.

I also tried tin snips, out of desperation, even though I knew it would make a deformed, roughly-cut mess (because tin snips always do). I didn’t bother photographing that train wreck.

The one thing I found that worked okay was a jigsaw with a very fine blade. The material has to be well supported and clamped close to the cut on both sides to keep from vibrating and deforming, but the resulting cut is actually fairly decent.

With the right clamping (screws and washers into scrap wood, in this case, and a good fence to ensure a straight cut, this does work. It’s very fussy to set up though, and there are still saw marks visible. This is an oh-kay solution, but I didn’t love it.

I made four strips with the jigsaw method and set about making some holes.

You can see the strips I cut with the jigsaw here, and I’ve marked them for the punch.

I went back to using the drill press for this, since it makes alignment trivial, and alignment is everything here. I felt really bad about doing this to my drill press, but the pressure required really isn’t that high if alignment is good and the punch is sharp.

When this works, it works pretty well!

Here are my four band clamp pieces with holes punched. I really wasn’t very happy with this result. The holes are poorly aligned because of the difficulty of using my punch without a proper press, and the saw-cut edges were bothering me. I decided to press on (pardon the pun).

To get the lengths of the band clamps just right, I set up the boiler on the surface plate and marked the “equator” all the way around with a height gage. Surface plate work is super fun and satisfying!

With the clamps cut to length and punched, it was time to braze in the bosses. To the fire bricks!

The brazing seemed to go pretty well. I had a really good fit for the bosses in the punched holes.

It took a few tries on each one, but I did manage to get a seemingly good braze joint all the way around each boss.

A test fit of the top band for one end seemed to suggest we were on a successful road.

This is the point where things started to go really wrong yet again.

I trimmed the halves of the bottom clamping section, but they were too short. A bolt had no hope of spanning that gap. I should have measured three times and cut once.

To make matters worse, while fitting the bottom clamp, all my braze joints to the ferrules on the top clamp started cracking and failing. 24ga sheet just wasn’t enough cross-sectional area for a secure braze, and the joints gave up the ghost under very little provocation. Recall also that I wasn’t happy with the pieces made thus far- misaligned holes, saw cut marks, etc. Everything was just sub-par overall.

I had used up all my brass sheet stock in all these various failed attempts at cutting, punching, brazing, etc. Each step in the process failed multiple times, and that’s usually a sign that the whole enterprise is on the wrong strategy. It was time for a stop-and-think, as my mom used to say.

I decided to start over with a different approach. I would not rely on brazing- the ferrules would clamp through the bands with screws. That would mean the clamps would have a sort of oblate-sphereoid shape to them, but the system would be secure, reliable, and easy to make. Second, I gave up on cutting nice brass strips, and simply ordered 1″ wide material. It felt like cheating, but the result is much nicer. Finally, I gave up on my homemade punch, since getting repeatable well-aligned holes with it was proving impossible.

My punch die got a second life as a drill guide. Using it to clamp down the material around the hole and drilling through it, combined with a sacrificial backer, I got perfect easy holes every time. Why didn’t I think of this sooner?

This time around, the bottom clamps were measured 48 times and cut once.

I made some little 10-24 nuts out of brass hex stock for the clamping bolt on the bottom bands.

With all the band clamp pieces remade (dimensions adjusted for my new bolt-through ferrule strategy), it was time for a test fit. “This one time, at band clamp…”

Shazam! That worked beautifully. The top band is solid and both ferrules pass through it. The bottom band is two parts, each with one ferrule passing through. The ferrules screw into the leg bosses to anchor the clamps, and the bottom clamp tightens the boiler upwards against the top band.

Here’s another angle showing how the bands overlap and join with the leg mounting bosses.

Here are all the parts that make up the leg system, to make it more clear.

Once I had a working system, making it again for the other end of the boiler was very very quick. The first set took two weeks to figure out and make. The second set took about 20 minutes. Funny how that goes.

Here it is sitting on all four legs for the first time. This was a very fine moment after a long and frustrating road trying to make this work.

The final step was to attach the legs to a brass plate. This plate serves to stiffen the whole leg system, and also protects the eventual wooden base under the boiler plant from the heat.

The band clamps tend to want to pull the feet outwards, which is good. They’ll get pulled inward by the base plate, putting the whole system in tension (and thus making it rigid). I pulled the feet inward with some string until everything was square, then measured that to know how to drill my holes in the base.

Result!

I could not be more pleased with how this leg system turned out. While it was a painful process, the end result was all the more satisfying for it.

Now we can get started making plumbing fittings and all the other bits and bobs that will make this empty shell into an actual boiler. Stay tuned!

The results from the first ever Reader Survey are in. My apologies if you didn’t get a chance to participate. It was only up for a couple of days, but the spam bots found it quickly and were starting to pollute the data. However, I got a very strong response in the opening hours, so I feel good about the quality of the results. I could have prevented the spam by requiring log-in to do the survey, but I didn’t want to do that because I know from my comment threads that there is a large silent majority of readers that prefer not to log in to WordPress. No problem- I get that. I wanted your voice to be heard here as well.

Many folks used the comment field to let me know they would contribute to the site if they knew how. Allow me to remedy that right now. The best way to support Blondihacks is via Patreon. Just click this big Patreon banner:

Patrons are charged per post, not on some time schedule. That incentivizes me to make more content, and protects you in case I go on vacation or have life stuff that gets in the way of blogging (which happens sometimes).

The second option is direct gifting through PayPal. Just click here:

My dream is to someday make Blondihacks pay the rent. It’s a long way from doing that right now, but every bit helps. There is roughly 40 hours of work that goes into every post on this site, and often hundreds of dollars in materials and tools. I spend 11 hours a day at my day job, then come home and spend my evenings working on this site. It’s a lot of effort, but I want to make it good.

If you feel the content is worthwhile and you’d like to see it continue, please consider supporting me.

Now, let’s take a look at the results from that survey. First up, the content of the articles.

People love all the things, as it turns out.

Those results are pretty strong. Most of you seem to like the variety here. That’s good, because I’m also all about variety. That will continue! There’s also a secondary preference for the electronics stuff. That makes sense, since much of the early traffic to the blog came from sites like Hack-a-Day and Adafruit. There’s a base of my audience still from there, I imagine. Lately things have expanded as my machine shop content has gained some interest, but don’t worry electronics fans- there will be more. I have a queue of interesting projects backed up in this area.

How about article frequency?

The technical term for this is “inconclusive”

On the frequency front, things are less clear. I suspect people voted here for different reasons. It would be interesting to segment this data, for example, on Patreon donors. They pay for the content everyone reads, and they pay per article. They are going to have a budget that doesn’t scale past some point. Someone who can afford to pay for one article per month from me might be unhappy if I suddenly started cranking out weekly content. Conversely, perhaps the readers who do not donate are mostly in the Often As Possible column. That’s rampant speculation, though. This data is all anonymous, and I have no way to segment or do further analysis. I expect the current rate of “roughly every 2-4 weeks when I have time” will continue.

On to the question of article length.

That’s comforting!

Seems that the bulk of the audience feels I have a sweet spot on length. That’s good to know. I try to aim for about a 5-10min read, depending on the number of pictures. Much longer and people wouldn’t finish. Much shorter and people wouldn’t feel value for their Patreon dollar. I try to strike that balance.

The final question may have come out of the blue for you all, but it’s something I’ve been thinking a lot about. All the cool kids do YouTube these days, and there’s opportunity there. However, producing video is immensely time consuming, and what I like about this is the writing. No matter what, the blog would continue, because writing is fun for me. Editing video is not very fun for me, but if people would pay for it, I might do it.

There’s some ambiguity here…

In surveys, the wording of the questions is everything. That’s why you should view all data reported in the media based on surveys with immense skepticism. You can pretty much get any audience to generate any data you want by how you word the questions. I think this YouTube thing is an example of a poorly worded question. There was overlap between the Yes answer and the Both answer. My intent was that “yes” meant you would support me dropping the blog completely and moving to YouTube. I suspect many people didn’t mean it that way, but it’s hard to know because I didn’t word the question well.

At the end of the day, I think the data shows there is interest in me doing video content, so I’ll continue to think about whether I have room in my schedule for it. If I do it, it would be exclusive paid content for Patreon supporters, perhaps using their new Lens system, or through a private YouTube.

If you’d like to keep in regular touch with me and my projects, follow me on Twitter. I post sneak peeks and in-progress shots of upcoming projects. Also sometimes cats.

Thanks again to all my readers who participated, and those who wanted to but got cut off by the spam bots. I was very surprised (even a little overwhelmed) at the volume of responses I got. If even a few percent of the people who responded became Patreon supporters, we could kick it up a notch around here.